(1) Filed of the Invention
This invention relates to an in-car sensor equipped with an aspirator fan motor, and more particularly to an in-car sensor equipped with an aspirator fan motor in an automotive air conditioner, which draws air from a predetermined position within a vehicle cabin to sample the temperature and humidity within the vehicle cabin.
(2) Description of the Related Art
Conventionally, some automotive air conditioners sample air temperature at a predetermined position within the vehicle cabin, and perform air conditioning such that the temperature within the vehicle cabin becomes equal to a preset temperature. As a device for detecting the air temperature within the vehicle cabin, an in-car sensor equipped with an aspirator fan motor is known. This in-car sensor equipped with an aspirator fan motor is comprised of a thermistor as a temperature-sensing element and an aspirator for forcibly drawing air from a predetermined position within the vehicle cabin to the thermistor. The aspirator is comprised of an aspirator fan for introducing air from the vehicle cabin to the thermistor, and a motor for driving the aspirator fan.
FIG. 3 is a central longitudinal cross-sectional view showing an example of a conventional in-car sensor equipped with an aspirator fan motor.
The conventional in-car sensor equipped with an aspirator fan motor includes an air inlet port 2 at a right-hand side of a casing 1 as viewed in the figure, which has an aspirator duct connected thereto, and an air outlet port 3 formed in the top of the casing 1. The aspirator fan motor 4 having a plurality of blades for producing an airflow from the air inlet port 2 to the air outlet port 3 is mounted in a central portion of the casing 1. A brushless motor excellent in quietness is used for a section of the aspirator fan motor 4. Space between the upstream side of the aspirator fan motor 4 and the air inlet port 2 forms a measurement chamber 5.
A mounting board 6 is arranged at the bottom of the casing 1. Mounted on the mounting board 6 are a thermistor 7 arranged within the measurement chamber 5 as a temperature-sensing element, and a brushless motor drive circuit for the aspirator fan motor 4. Further, the mounting board 6 is connected to contact pins 9 of a connector 8 formed at a left-hand side of the casing 1 as viewed in the figure. These contact pins 9 are connected to the output terminals of the thermistor 7, the power terminals of the brushless motor drive circuit, etc.
In the in-car sensor equipped with an aspirator fan motor constructed as above, when the aspirator fan motor 4 is rotated, an airflow is produced from the air inlet port 2 to the air outlet port 3. Accordingly, the thermistor 7 arranged within the measurement chamber 5 detects the temperature of air from within the vehicle cabin which flows thereto via the air inlet port 2. A signal indicative of the temperature detected by the thermistor 7 is supplied to the control system of an automotive air conditioner, not shown, arranged outside the sensor, via the contact pins 9 of the connector 8, and used for control of the temperature within the vehicle cabin.
Further, in some cases, to allow the automotive air conditioner to perform air conditioning such that the passenger compartment within the vehicle cabin is more comfortable, the humidity within the vehicle cabin is detected to perform the air conditioning control of the inside of the vehicle cabin in a manner adapted to lots of possible cases. To this end, a humidity sensor is conventionally arranged e.g. at a rear seat within the vehicle cabin, for detecting the humidity within the vehicle cabin.
FIG. 4 is a cross-sectional view of a conventional humidity sensor.
The humidity sensor includes a humidity-sensing element 11 and a conversion circuit 12, which are mounted on a mounting board 13, and accommodated within a casing 14. The casing 14 is formed with a plurality of circulation holes 15 for spontaneous ventilation of air from the vehicle cabin into the casing 14. Connected to the mounting board 13 is a cable 16 comprised of an output signal line and a power line connected to the control system of the automotive air conditioner. Further, the humidity sensor is mounted at a humidity-measuring position within the vehicle cabin, with mounting screws 17.
As the humidity-sensing element 11 mounted on the mounting board 13, various types are known. In the illustrated example, a capacitance type sensor is used. The humidity-sensing element 11 of the capacitance type is comprised of a humidity-sensitive high-polymer membrane formed on a silicon substrate, and electrodes formed on the surfaces of the silicon substrate and the humidity-sensitive high-polymer membrane. The humidity-sensitive high-polymer has a dielectric constant far smaller than that of water, and has a characteristic that the dielectric constant thereof largely increases as it absorbs moisture. To regard this characteristic as changes in the dielectric capacitance, the humidity can be measured. Therefore, a signal from the humidity-sensing element 11 cannot be directly used differently from that from the temperature-sensing element formed by the thermistor 7, and hence, the conversion circuit 12 detects and converts changes in the capacitance into a type of signal which can be handled by the control system of the automotive air conditioner. As the conversion circuit 12, there is generally used a circuit that converts a change in the capacitance, i.e. a change in humidity, into a voltage signal or a frequency signal proportional to the change.
As described above, to detect humidity within the vehicle cabin, the conventional automotive air conditioner necessitates a place where the humidity sensor is mounted, and hence it has been proposed to mount a thermistor for detecting temperature and a humidity sensor together on the in-car sensor equipped with an aspirator fan motor (Japanese Laid-Open Patent Publication (Kokai) No. 62-110521 and Japanese Laid-Open Patent Publication (Kokai) No. 2000-351312). This makes it possible to reduce the cost of the automotive air conditioner by making the same no longer necessitate a mounting place or mounting work for the humidity sensor.
However, in the conventional automotive air conditioner, the humidity sensor necessitates a conversion circuit, by its principle, and therefore, requires provision of a power supply and an element coping with electromagnetic interference for the humidity sensor, which increases the cost of the automotive air conditioner.
The present invention has been made in view of these points, and an object thereof is to provide a low-cost in-car sensor equipped with an aspirator fan motor, which includes a temperature sensor and a humidity sensor.
To solve the above problem, there is provided an in-car sensor equipped with an aspirator fan motor, for drawing air from within a vehicle cabin of a vehicle and outputting signals of temperature and humidity necessary for control of an automotive air conditioner, the in-car sensor comprising a mounting board on which electronic circuit components are mounted for driving the aspirator fan motor, a temperature sensor mounted at a desired position between an air inlet port and an air outlet port on the mounting board, for detecting a temperature of the air drawn from within the vehicle cabin, and a humidity sensor mounted at a desired position between the air let port and the air outlet port of the mounting board, for detecting a humidity of the air drawn from within the vehicle cabin, wherein electronic circuit components necessary for operation of the humidity sensor are provided by shared use of the electronic circuit components for driving the aspirator fan motor.
According to the in-car sensor equipped with an aspirator fan motor, electronic circuit components, such as a power supply circuit and an element coping with electromagnet interference, which has been necessitated by the humidity sensor are provided by the shared used of the electronic circuit components, such as a power supply circuit and an element coping with electromagnet interference, which have been employed in a drive circuit of the aspirator fan motor. This makes it possible to reduce the number of electronic circuit components necessary for the humidity sensor, and provide a more inexpensive automotive air conditioner.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.